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Abstract:

The present invention discloses a quaternary vertical light emitting
diode with double surface roughening and a manufacturing method thereof,
where a Bragg reflective layer is formed on a substrate; a first type of
epitaxial layer is formed on the Bragg reflective layer; a light emitting
layer is formed on the first type of epitaxial layer; a second type of
epitaxial layer is formed on the light emitting layer; a first GaP window
layer with small circular holes or in a mesh structure is formed on the
second type of epitaxial layer; a second GaP window layer with small
circular holes or in a mesh structure is formed on the first GaP window
layer; a first electrode is formed on the top surface of the second GaP
window layer; and a second electrode is formed on the bottom surface of
the GaAs substrate. After conventional processes, the invention forms the
alternating small circular holes or the mesh structure between the first
GaP window layer and the second GaP window layer to change a light path
along which light emitting from the light emitting layer reaches the
surface of a light emitting diode die so that more of light emits from
inside and the light extracting rate of the invention is 20% higher than
that of an existing light emitting diode.

Claims:

1. A quaternary vertical light emitting diode with double surface
roughening, comprising: a Bragg reflective layer formed on a substrate; a
first type of epitaxial layer formed on the Bragg reflective layer; a
light emitting layer formed on the first type of epitaxial layer; a
second type of epitaxial layer formed on the light emitting layer; a
first GaP window layer with small circular holes or in a mesh structure
formed on the second type of epitaxial layer; a second GaP window layer
with small circular holes or in a mesh structure formed on the first GaP
window layer; a first electrode formed on the top surface of the second
GaP window layer; and a second electrode formed on the bottom surface of
the GaAs substrate.

2. The quaternary vertical light emitting diode with double surface
roughening according to claim 1, wherein the thickness of the first GaP
window layer ranges from 1 to 3 μm, wherein in the first Gap window
layer, the diameter of the small circular holes or the width of the
channels in the mesh structure ranges from 2 to 4 μm, and the small
circular holes or the channels are spaced at an interval ranging from 3
to 5 μm.

3. The quaternary vertical light emitting diode with double surface
roughening according to claim 1, wherein the thickness of the second GaP
window layer ranges from 5 to 7 μm, wherein in the second GaP window,
the diameter of the small circular holes or the width of the channels in
the mesh structure ranges from 2 to 4 μm, and the small circular holes
or the channels are spaced at an interval ranging from 3 to 5 μm.

4. A method for manufacturing a quaternary vertical light emitting diode
with double surface roughening, comprising the steps of: 1) growing
epitaxially and forming a distributed Bragg reflective layer, a first
type of epitaxial layer, a light emitting layer and a second type of
epitaxial layer on a substrate sequentially; 2) forming a first GaP
window layer on the second type of epitaxial layer; 3) forming a mesh
structure consisted of patterns of small circular holes or channels in
the first GaP window layer by a wet or dry etch method; 4) forming a
second GaP window layer on the first GaP window; 5) forming a mesh
structure consisted of patterns of small circular holes or channels in
the second GaP window layer by a wet or dry etch method to arrange the
patterns of the first GaP window layer and the second GaP window layer
alternately without overlapping; 6) forming a first electrode on the top
surface of the second GaP window layer and a second electrode on the
bottom surface of the substrate; and 7) dicing into quaternary vertical
light emitting diodes.

5. The method for manufacturing a quaternary vertical light emitting
diode with double surface roughening according to claim 4, wherein the
material of the substrate is selected from any one or combination of GaAs
and GaP.

6. The method for manufacturing a quaternary vertical light emitting
diode with double surface roughening according to claim 4, wherein the
thickness of the first GaP window layer ranges from 1 to 3 μm, wherein
in the first Gap window layer, the diameter of the small circular holes
or the width of the channels in the mesh structure ranges from 2 to 4
μm, and the small circular holes or the channels are spaced at an
interval ranging from 3 to 5 μm.

7. The method for manufacturing a quaternary vertical light emitting
diode with double surface roughening according to claim 4, wherein the
thickness of the second GaP window layer ranges from 5 to 7 μm,
wherein in the second GaP window, the diameter of the small circular
holes or the width of the channels in the mesh structure ranges from 2 to
4 μm, and the small circular holes or the channels are spaced at an
interval ranging from 3 to 5 μm.

8. The method for manufacturing a quaternary vertical light emitting
diode with double surface roughening according to claim 4, wherein an
etching solution for the wet etch method is selected from any one or
combination of HF, NH4F, CH3COOH, H2SO4 and
H2O.sub.2.

9. The method for manufacturing a quaternary vertical light emitting
diode with double surface roughening according to claim 4, wherein an
etching gas for the dry etch method is selected from any one or
combination of Ar2, O2, BCl3, Cl2 and SiCl.sub.4.

Description:

FIELD OF THE INVENTION

[0001] The present invention relates to a quaternary light emitting diode
and in particular to a quaternary vertical light emitting diode with
double surface roughening and a manufacturing method thereof.

BACKGROUND OF THE INVENTION

[0002] At present, light emitting diodes have been applied widely in
economic life, for example, display, decoration, communication, etc., and
their general structure typically includes a substrate, a distributed
Bragg reflective layer, a first type of epitaxial layer, a light emitting
layer, a second type of epitaxial layer, a window layer, a first
electrode and a second electrode. The window layer of an existing
vertically structured quaternary AlGaInP light emitting diode is
typically structured as a single GaP layer with a planar upper surface,
so when the light emitting layer acting as an interlayer emits light, a
part of light emits towards the outside of the element and most of light
may be subject to total reflection to thereby result in a poor emergence
effect of light. Due to a semiconductor material which is a material with
a high refractive index relative to the ambient air, total reflection
will be caused when a emergence angle of light is larger than a certain
critical angle; and also totally reflected light may generate heat inside
the light emitting diode so that the overall temperature of the light
emitting diode will rise, thus greatly degrading the reliability of the
product.

[0003] In order to alleviate the problem of most of light being totally
reflected due to the significant difference between high and low
refractive indexes, some researchers have proposed the use of a P-GaN
surface roughening method to rough the interface regularly so that part
of totally reflected light can emerge in the form of scattered light to
thereby improve the light extracting rate, but direct roughening of the
top surface of an LED may cause some damage to an active layer and a
transparent electrode and also render the LED difficult to manufacture.

SUMMARY OF THE INVENTION

[0004] In order to address the foregoing problem, the invention is
intended to provide a quaternary vertical light emitting diode with
double surface roughening and a manufacturing method thereof

[0005] In a technical solution adopted according to the invention to
address the technical problem thereof, a quaternary vertical light
emitting diode with double surface roughening includes: a Bragg
reflective layer formed on a substrate; a first type of epitaxial layer
formed on the Bragg reflective layer; a light emitting layer formed on
the first type of epitaxial layer; a second type of epitaxial layer
formed on the light emitting layer; a first GaP window layer with small
circular holes or in a mesh structure formed on the second type of
epitaxial layer; a second GaP window layer with small circular holes or
in a mesh structure formed on the first GaP window layer; a first
electrode formed on the top surface of the second GaP window layer; and a
second electrode formed on the bottom surface of the substrate.

[0006] A method for manufacturing a quaternary vertical light emitting
diode with double surface roughening includes the steps of:

[0007] 1) growing epitaxially and forming a distributed Bragg reflective
layer, a first type of epitaxial layer, a light emitting layer and a
second type of epitaxial layer on a substrate sequentially;

[0008] 2) forming a first GaP window layer on the second type of epitaxial
layer;

[0009] 3) forming a mesh structure consisted of patterns of small circular
holes or channels in the first GaP window layer by a wet or dry etch
method;

[0010] 4) forming a second GaP window layer on the first GaP window;

[0011] 5) forming a mesh structure consisted of patterns of small circular
holes or channels in the second GaP window layer by a wet or dry etch
method to arrange the patterns of the first GaP window layer and the
second GaP window layer alternately without overlapping;

[0012] 6) forming a first electrode on the top surface of the second GaP
window layer and a second electrode on the bottom surface of the
substrate; and

[0014] According to the invention, the material of the substrate is
selected from any one or combination of GaAs and GaP; the thickness of
the first GaP window layer ranges from 1 to 3 μm, wherein the diameter
of the small circular holes or the width of the channels in the mesh
structure ranges from 2 to 4 μm, and the small circular holes or the
channels are spaced at an interval ranging from 3 to 5 μm; the
thickness of the second GaP window layer ranges from 5 to 7 μm,
wherein the diameter of the small circular holes or the width of the
channels in the mesh structure ranges from 2 to 4 μm, and the small
circular holes or the channels are spaced at an interval ranging from 3
to 5 μm; an etching solution for the wet etch method is selected from
any one or combination of HF, NH4F, CH3COOH, H2SO4
and H2O2; and an etching gas for the dry etch method is
selected from any one or combination of Ar2, O2, BCl3,
Cl2 and SiCl4.

[0015] As compared with the prior art, after conventional processes, the
invention forms the alternating small circular holes or the mesh
structure between the first GaP window layer and the second GaP window
layer to change a light path along which light emitting from the light
emitting layer reaches the surface of a light emitting diode die so that
more of light is extracted from inside and the light extracting rate of
the light emitting diode is 20% higher than in the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a schematic sectional view of a quaternary vertical light
emitting diode with double surface roughening according to the invention.

[0017] FIG. 2 is a top view of the quaternary vertical light emitting
diode with double surface roughening according to the invention.

[0019] The invention will be further described hereinafter with reference
to the drawings and embodiments thereof.

[0020] As illustrated in FIG. 1, in a method for manufacturing a
quaternary vertical light emitting diode with double surface roughening,
a process of manufacturing the same includes the following steps:

[0021] A distributed Bragg reflective layer 2, a first type of epitaxial
layer 3, a light emitting layer 4 and a second type of epitaxial layer 5
are grown epitaxially and formed on a GaAs substrate 1 sequentially.

[0022] A first GaP window layer 6 is formed on the second type of
epitaxial layer 5, wherein a thickness of the first window layer 6 is 2
μm.

[0023] The first GaP window layer 6 is etched in a wet etch method with an
etching solution consisted of HF, NH4F, CH3COOH,
H2SO4 and H2O2 to form therein a mesh structure
consisted of small circular holes, wherein a diameter of the small
circular hole is 4 μm and the small circular holes are spaced at an
interval of 3 μm.

[0024] A second GaP window 7 with a thickness of 6 μm is formed on the
first GaP window layer 6.

[0025] The second GaP window layer 7 is etched in a dry etch method with
an etching gas consisted of Ar2, O2, BCl3, Cl2 and
SiCl4 to form therein a mesh structure consisted of small circular
holes so as to arrange patterns of the first GaP window 6 and the second
GaP window 7 alternately without overlapping wherein a diameter of the
small circular hole is 3 μm and the small circular holes are spaced at
an interval of 4 μm.

[0026] A first electrode 8 is formed on the top surface of the second GaP
window 7, and a second electrode 9 is formed on the bottom surface of the
substrate 1.

[0028] As illustrated in FIG. 1, a quaternary vertical light emitting
diode with double surface roughening manufactured according to the above
method includes: a GaAs substrate 1; a distributed Bragg reflective layer
2 formed on the GaAs substrate 1; a first type of epitaxial layer 3
formed on the distributed Bragg reflective layer 2; a light emitting
layer 4 formed on the first type of epitaxial layer 3; a second type of
epitaxial layer 5 formed on the light emitting layer 4; a first GaP
window layer 6 in a mesh structure consisted of small circular holes
formed on the second type of epitaxial layer 5; a second GaP window layer
7 in a mesh structure consisted of small circular holes formed on the
first GaP window layer 6; a first electrode 8 formed on the top surface
of the second GaP window layer 7; and a second electrode 9 formed on the
bottom surface of the GaAs substrate 1.

[0029] As can be apparent from FIG. 1 and FIG. 2, light emitting from the
light emitting layer 4 firstly passes the interface between the first GaP
window layer 6 and the second GaP window layer 7 to be scattered due to
the mesh structure consisted of the small circular holes on the first GaP
window layer 6, and thereafter light passes the interface between the
second GaP window layer 7 and the air to be scattered again due to the
mesh structure consisted of the small circular holes on the second GaP
window layer 7, thereby greatly improving the light extracting rate of
the light emitting diode.

[0030] The foregoing embodiments are provided to merely illustrate but not
limit the invention, and those ordinarily skilled in the art can further
make various modifications or variations without departing from the
spirit and scope of the invention. Accordingly all equivalent technical
solutions come to the scope of the invention as defined in the appended
claims.